[PATCH] proc: Rewrite the proc dentry flush on exit optimization

[linux-2.6] / kernel / stop_machine.c

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index c39ed70af1740e79f0d0032b711d40516013c650..2c0aacc37c5513b0a3898f49e937683501f66ae2 100644 (file)
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -4,6 +4,7 @@
 #include <linux/cpu.h>
 #include <linux/err.h>
 #include <linux/syscalls.h>
+#include <linux/kthread.h>
 #include <asm/atomic.h>
 #include <asm/semaphore.h>
 #include <asm/uaccess.h>
@@ -25,15 +26,13 @@ static unsigned int stopmachine_num_threads;
 static atomic_t stopmachine_thread_ack;
 static DECLARE_MUTEX(stopmachine_mutex);
 
-static int stopmachine(void *cpu)
+static int stopmachine(void *unused)
 {
        int irqs_disabled = 0;
        int prepared = 0;
 
-       set_cpus_allowed(current, cpumask_of_cpu((int)(long)cpu));
-
        /* Ack: we are alive */
-       mb(); /* Theoretically the ack = 0 might not be on this CPU yet. */
+       smp_mb(); /* Theoretically the ack = 0 might not be on this CPU yet. */
        atomic_inc(&stopmachine_thread_ack);
 
        /* Simple state machine */
@@ -43,14 +42,14 @@ static int stopmachine(void *cpu)
                        local_irq_disable();
                        irqs_disabled = 1;
                        /* Ack: irqs disabled. */
-                       mb(); /* Must read state first. */
+                       smp_mb(); /* Must read state first. */
                        atomic_inc(&stopmachine_thread_ack);
                } else if (stopmachine_state == STOPMACHINE_PREPARE
                           && !prepared) {
                        /* Everyone is in place, hold CPU. */
                        preempt_disable();
                        prepared = 1;
-                       mb(); /* Must read state first. */
+                       smp_mb(); /* Must read state first. */
                        atomic_inc(&stopmachine_thread_ack);
                }
                /* Yield in first stage: migration threads need to
@@ -62,7 +61,7 @@ static int stopmachine(void *cpu)
        }
 
        /* Ack: we are exiting. */
-       mb(); /* Must read state first. */
+       smp_mb(); /* Must read state first. */
        atomic_inc(&stopmachine_thread_ack);
 
        if (irqs_disabled)
@@ -77,7 +76,7 @@ static int stopmachine(void *cpu)
 static void stopmachine_set_state(enum stopmachine_state state)
 {
        atomic_set(&stopmachine_thread_ack, 0);
-       wmb();
+       smp_wmb();
        stopmachine_state = state;
        while (atomic_read(&stopmachine_thread_ack) != stopmachine_num_threads)
                cpu_relax();
@@ -85,26 +84,28 @@ static void stopmachine_set_state(enum stopmachine_state state)
 
 static int stop_machine(void)
 {
-       int i, ret = 0;
+       int ret = 0;
+       unsigned int i;
        struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
-       mm_segment_t old_fs = get_fs();
 
        /* One high-prio thread per cpu.  We'll do this one. */
-       set_fs(KERNEL_DS);
-       sys_sched_setscheduler(current->pid, SCHED_FIFO,
-                               (struct sched_param __user *)&param);
-       set_fs(old_fs);
+       sched_setscheduler(current, SCHED_FIFO, &param);
 
        atomic_set(&stopmachine_thread_ack, 0);
        stopmachine_num_threads = 0;
        stopmachine_state = STOPMACHINE_WAIT;
 
        for_each_online_cpu(i) {
-               if (i == _smp_processor_id())
+               struct task_struct *tsk;
+               if (i == raw_smp_processor_id())
                        continue;
-               ret = kernel_thread(stopmachine, (void *)(long)i,CLONE_KERNEL);
-               if (ret < 0)
+               tsk = kthread_create(stopmachine, NULL, "stopmachine");
+               if (IS_ERR(tsk)) {
+                       ret = PTR_ERR(tsk);
                        break;
+               }
+               kthread_bind(tsk, i);
+               wake_up_process(tsk);
                stopmachine_num_threads++;
        }
 
@@ -119,13 +120,12 @@ static int stop_machine(void)
                return ret;
        }
 
-       /* Don't schedule us away at this point, please. */
-       local_irq_disable();
-
        /* Now they are all started, make them hold the CPUs, ready. */
+       preempt_disable();
        stopmachine_set_state(STOPMACHINE_PREPARE);
 
        /* Make them disable irqs. */
+       local_irq_disable();
        stopmachine_set_state(STOPMACHINE_DISABLE_IRQ);
 
        return 0;
@@ -135,6 +135,7 @@ static void restart_machine(void)
 {
        stopmachine_set_state(STOPMACHINE_EXIT);
        local_irq_enable();
+       preempt_enable_no_resched();
 }
 
 struct stop_machine_data
@@ -182,7 +183,7 @@ struct task_struct *__stop_machine_run(int (*fn)(void *), void *data,
 
        /* If they don't care which CPU fn runs on, bind to any online one. */
        if (cpu == NR_CPUS)
-               cpu = _smp_processor_id();
+               cpu = raw_smp_processor_id();
 
        p = kthread_create(do_stop, &smdata, "kstopmachine");
        if (!IS_ERR(p)) {